In the 1970s and 1980s printer manufacturers such as Hewlett-Packard and Cannon began working on technology to replace dot matrix printers. By the 1990s inkjet printers and associated cartridges were commonly used. The term “inkjet” defines any printer that creates a printed image by firing extremely small droplets of ink onto the printer paper. Generally, the droplets of ink that produce the printed image are extremely small (between 10 and 30 droplets per millimeter), and positioned precisely. In a simple view of an inkjet printer, the ink droplets are drawn into a printhead from a printhead reservoir fluidly coupled to an ink tank. The droplets are then ejected out thru nozzles onto the paper. The printhead scans the page using a stepper motor assembly to move it back and forth along a stabilizer bar horizontally as it operates.
Inkjet technology is often classified as either continuous or drop-on-demand. A continuous technology is one in which a continuous stream of ink droplets are sprayed onto a page. Because continuous stream printers typically spray droplets at speeds exceeding one million droplets per second, these printers are extremely fast. Continuous printing, however, is expensive because there is an excessive amount of wasted ink. This is especially problematic in high resolution printers.
Drop-on-demand printers have emerged to solve at least some of the problems associated with continuous printing. Drop-on-demand printers release ink droplets only as required. Drop-on-demand technology works by forcing small droplets of ink onto print media, through nozzles. The amount of ink propelled onto the page through the ink cartridge is determined by the driver software, which dictates which nozzles shoot droplets, and when. In terms of speed, on most inkjet printers, the print head takes about half a second to print a strip across an 8.5″ page.
Drop-on-demand printers generally use either a thermal bubble or piezo-electric technology to force droplets out of the nozzles of the print head. U.S. Pat. No. 5,278,584 to Hewlett-Packard (January 1994) teaches a thermal bubble technology in which a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. The substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, a bubble is created causing an ink droplet to be ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the print head moves across the page, the ink is expelled in a pattern on the media. A particular limitation of the thermal process is that ink should be generally heat resistant. Furthermore, the heating process creates a need for a cooling process.
Piezo-electric technology is being used by some manufacturers, such as Epson, as an alternative to thermal. A piezo-electric technology uses a crystal that reacts to an electric charge to force out droplets. In response to the charge, the crystal vibrates or expands forcing a precise amount of ink from the print head. U.S. Pat. No. 5,719,607 to Seiko Epson Corporation (February, 1998) teaches a piezo system in which a piezo-electric element is used to control secretion of ink droplets. One persisting problem with print cartridges and particularly a system using a piezo element system is the high cost to make the print cartridges. This high manufacturing cost translates into a high maintenance cost for a user.
Because some printers use piezo and some use thermal there are a wide variety of print cartridges, and therefore selection of a replacement cartridge can be a tedious and time consuming activity. Additionally, there are many carriage/printhead/ink tank configurations that add to the complexity of buying replacement cartridges. Some models incorporate signal drivers in the printer electronics and some models incorporate signal drivers in the printhead on the cartridge. As a result of the need for a specialized cartridge, consumers are at the mercy of the cartridge manufacturers that charge excessively high prices for the cartridges.
Thus, there is a need for print cartridges that are more versatile and adaptable to the many different printer configurations.